Vat dyeing of polypropylene



Unite States The present invention relates to aprocess for dyeing fibers of stereoregular polypropylene. More particularly, it relates to a process for dyeing stereoregular polypropylene fibers with vat dyestuffs.

It is well known in the art of dyeing that one of the most diificult problems involved in the development of any new fiber is the discovery of satisfactory methods for dyeing the fiber. In fact, it has been necessary each time a new fiber is introduced to devise entirely new methods, and sometimes even new dyestuffs, for dyeing it.

One of the new fibers that has been introduced recently to the trade is made from stereoregular polypropylene, a highly crystalline polymer that melts in the range of about 165 to 172 C. The dyeing of polypropylene fiber has been recognized as an especially difficult problem because of the extremely hydrophobic nature of the polymer and the absence of functional groups in its structure. There fore, just as in the case of other synthetic fibers that have been introduced in the past, the dyeing of polypropylene fiber presents special problems and difficulties that must be overcome. This has been particularly true with respect to attempts made to dye polypropylene fiber with vat dyestuffs. Since the fiber is strongly hydrophobic, the aqueous dyeing baths used in vat dyeing wet the fiber only superficially but do not penetrate the inside of the fiber. Accordingly, conventional methods for dyeing cotton and cellulosic materials with vat dyestuffs from a highly alkaline vat are not satisfactory for this new fiber.

A primary object of the present invention is to provide a process for dyeing polypropylene fiber with vat dyestuffs. The invention, which meets this objective, is based upon the discovery that polypropylene fiber can be vat dyed in ate medium to deep shades by carrying out the dyeing in the presence of an amine having the formula RNH in which R is a hydrocarbon radical of from 8 to 22 carbon atoms, more preferably from about 12 to 20 carbon atoms, in a dyebath having a pH within the range of about 6 to 10.

Both the presence of the hydrocarbon amine and the recited pH of the dyebath are necessary elements of the invention. Either the omission of the amine from the process or a departure from the recited pH results in dyeings of a lighter shade and poor fastness to light.

The hydrocarbon amines that are employed in the process of the invention normally are added to the dyebath in the form of a carboxylic acid salt to facilitate the dispersion of the amine in the dyebath. Of course, when the dyebath is alkaline, as is permissible in the invention, the amine will not exist as a carboxylic acid salt but rather as free amine. Obviously, the amine can be introduced into the dyebath in various ways. For instance, it can be added directly to the dyebath and dispersed therein by stirring or it can be impregnated on the fiber to be dyed and thus introduced into the dyebath coincidentally with the fiber.

Although the function of the amine is not understood, it is believed to act as a carrier or dyeing assistant by depositing itself on the surface of the fiber. The dyestuff which, in the process of the invention, exists partly or wholly in an acid leuco form, is believed to be attracted to and probably dissolves in the amine and then migrates into the body of the fiber. Subsequent oxidation of the dyestuff in the normal manner insolubilizes and locks the dye in the fiber. Whatever may be the action of the amine in promoting good dyeing, it has been determined ice that other agents having surface active properties are incapable of bestowing the same benefit. For instance, fatty alcohol sulfates, sulfonated oils, and sodium salts of alkylbenzene sulfonates not only fail to improve dyeing when used in the same way that hydrocarbon amines are used in this invention but often even detract from the quality of the dyeing.

The following examples are presented to illustrate the invention. Parts and percentages are by weight unless otherwise specified.

Example 1 A vat dyebath was prepared by dispersing 12 g. of Sandothrene Brilliant Green NBF Paste (Cl No. 59825) in 500 m1. of water to which had been added 10 ml. of a 10% aqueous solution of dehydroabietylamine acetate. There was then added ml. of a 4% aqueous sodium hydroxide solution while stirring. The bath was then warmed to 65-75 C. and about 5 g. of sodium hydrosulfite was added to reduce the vat. Sufficient water was then added to give a total volume of 1250 ml. followed by the addition of sufficient sodium bicarbonate to lower the pH of the bath to 8-9. A skeiu of yarn which had been spun from stereoregular polypropylene having a reduced specific viscosity of 3 and a crystalline melting point of 167 C. was immersed in the dyebath for a period of one hour while gradually raising the temperature of the bath to C. and periodically turning the skein to improve the uniformity of distribution of the dye. Upon removal from the bath the skein Was squeezed to remove excess liquid and was then oxidized by subjection for 10 minutes to a stream of air while suspended in vapors from a steam bath. Oxidation was completed by immersing the skein in a 2% aqueous solution of sodium perborate at 8090 C. for 10 minutes. The skein was then scoured with hot water containing sodium dodecylbenzene sulfonate.

A medium to dark green dyeing was achieved. The dyeing retained its full depth of color after immersion for 4 hours in perchloroethylene, after 5 average commercial lannderings, and after exposure for hours in a Fade- Ometer.

Example 2 This example was carried out in exactly the same manner as Example 1 with the exception that the aqueous solution of dehydroabietylamine acetate was replaced with 20 ml. of a 5% aqueous solution of coco amine acetate. The resultant dyeing was of the same shade as that of Example 1 and possessed the same fastness.

Example 3 This example was the same as Example 1 except that the aqueous solution of dehydroabietylamine was replaced with 20 m1. of a 5% aqueous solution of hydrogenated tallow amine acetate. The resultant dyeing was of the same shade as that of Example 1 and possessed the same fastness.

Example 4 In this example the procedure of Example 1 was modified by replacing the dehydroabietylamine acetate with 10 ml. of a 7% aqueous solution of a mixture of C to C tertiary alkylamines and by carrying out the last 15 minutes of dyeing at the boiling point of the bath. The dyeing was equivalent to that obtained in Example 1.

Example 5 This example was carried out in the same manner as Example 4 with the modification that the pH of the dyebath was adjusted to 6-7 by addition of dilute acetic acid before dyeing. The dyeing was equivalent to Example 4.

Example 6 This example was carried out according to the procedure of Example 4 but substituting 7.5 g. of Sandothrene Dark Blue NR paste (CI. 59815) for the Sandothrene Brilliant Green NBF paste. A deep purple dyeing was attained that had excellent fastness to dry cleaning, laundering and light.

Example 7 This example was carried out according to the procedure of Example 4 with the substitution of 7.5 g. of Ciba Brilliant Pink R paste (CI. 73360) for the Sandothrene Brilliant Green NBF paste. A medium pink dye resulted. The dyeing was fast to 4 hours immersion to perchloroethylene and showed no fading after 60 hours in a Fade- Ometer.

Example 8 The procedure of Example 1 was repeated using 7.5 g. of Calcoloid Violet 6RD paste ((3.1. 73385) in place of Sandothrene Brilliant Green NBF paste. A deep violet dyeing was attained that possessed excellent fastness to laundering, dry cleaning and light.

Example 9 The procedure of Example 1 was followed with the substitution of 7.5 g. Sandothrene Yellow NGPA in place of the Sandothrene Brilliant Green NBF paste. A deep yellow dyeing of excellent fastness to light, laundering and dry cleaning resulted.

Example 10 A skein of the polypropylene yarn as used in previous examples and weighing about 30 g. was immersed in 500 ml. of a 0.25% aqueous solution of dehydroabietylamine acetate and then heated in steam at 1 l C. for 15 minutes. The skein was then dried and dyed according to the procedure of Example 1 using 7.5 g. of Calcoloid Brown RRP paste (CI. 73410) in place of Sandothrene Brilliant Green paste and omitting the dehydroabietylamine from the dyebath recipe. The skein was dyed an even, rich medium brown shade. It had a Fade-Ometer life of 96 hours and the dyeing was fast to laundering and dry cleaning.

The examples show that excellent dyeings that are fast to light, laundering and dry cleaning are obtainable by the process of the invention. Additional experiments have shown that both the recited pH of the dyebath and the presence of a hydrocarbon amine are necessary to assure the excellent quality of dyeing. When using a dyebath of pH 1112, for instance, as is conventional when dyeing cotton and other cellulosic fibers, the same dyeing procedure even in the presence of a hydrocarbon amine results in dyeings of only a pastel shade and very poor fastness to light. On the other hand when the dyebath has an initial pH below 6, there is excessive precipitation of dye and resultant poor dyeings. Similarly, the amine is beneficial in assuring the attainment of dyeings of medium to deep shades that are fast to light.

The process is applicable to fiber of stereoregular polypropylene in the form of staple or continuous filament and may be applied to the fiber as individual filaments or as skeins of yarn or in the form of cloth. Blends of such fiber with other fibers can also be dyed by the process.

As previously explained, the action of the amine in the process of the invention appears to be of a physical nature which is a result of its relatively long hydrocarbon, hence hydrophobic, chain, attached to the relatively hydropholic NH group. Consequently, the nature of the hydrocarbon substituent, i.e., whether it be saturated or unsaturated, aliphatic or aromatic, is not important. Thus, any primary amine in which the substituent is a hydrocarbon radical of 8 to 22 carbon atoms is useful in the invention. Typical amines of this class are n-octyl amine, n-decyl amine, n-dodecyl amine, octadecyl amine, oleyl amine, naphthyl amine, t-octyl amine, dehydroabietyl amine, tallow amine, hydrogenated tallow amine, coco amine, tall oil amine, and the like.

Vat dyes of either the indigoid or anthraquinone type can be used in the invention and the preparation of the dyebath and the manipulative procedure of dyeing are techniques already well known in the art except, of course, that a hydrocarbon amine must be present in the dyebath and the pH must be adjusted as previously described.

Illustrating a typical procedure a dyebath can be prepared by dispersing the dye in water at the rate of about 1 to 6 oz. of commercially available paste and then incorporating in the dyebath from about 0.05 to 0.3 oz. of hydrocarbon amine per gallon of water. Caustic soda is then added to the dyebath and the dye is then reduced by the addition of sodium hydrosulfite in conventional manner. In accordance with the invention the pH of the bath is next adjusted to 6 to 10 with a suitable acid such as sodium bicarbonate or acetic acid. Dyeing is then carried out by immersing the fiber in the bath. Ordinarily the temperature of the dyebath should be at least about 60 C., but the maximum temperature is a matter of convenience. Normally, the temperature in the dyebath will not exceed its atmospheric boiling point although by employing pressure vessels for dyeing, it is possible and feasible to increase the dyebath temperature to as high as about C. without detracting from the quality of the dyeing. The fiber upon removal from the bath is then oxidized and secured in conventional manner.

Obviously, many modifications in the above procedure can be made without departing from the scope of the invention. One such modification disclosed in the examples comprises impregnating the fiber with the hydrocarbon amine rather than introducing the amine by itself to the dyebath. Another modification comprises first depositing the unreduced dye and the amine 0n the fiber and then immersing the treated fiber in a bath to which is added caustic soda and sodium hydrosulfite followed by adjustment to the required pH. All of these techniques are Well known in the dyeing art and require no elaboration.

What I claim and desire to protect by Letters Patent is:

1. In the dyeing of fiber of stereoregular polypropylene with vat dyes, the improvement which comprises dyeing the fiber in an aqueous dyebath at a pH of 6 to 10 in the presence of an amine having the formula RNH wherein R is a hydrocarbon radical of about 8 to 22 carbons.

2. The process of claim 1 in which the amine is coco amine.

3. The process of claim 1 in which the amine is dehydroabietylamine.

4. The process of claim 1 in which the genated tallow amine.

amine is hydro- Reterences Cited in the file of this patent UNITED STATES PATENTS 2,074,380 Flett Mar.'23, 1937 2,256,808 Kern Sept. 23, 1941 2,774,647 Mecco et al Dec. 18, 1956 2,890,093 Mautner June 9, 1959 

1. IN THE DYEING OF FIBER OF STEREOREGULAR POLYPROPYLENE WITH VAT DYES, THE IMPROVEMENT WHICH COMPRISES DYEING THE FIBER AND AN AQUEOUS DYEBATH AT A PH OF 6 TO 10 IN THE PRESENCE OF AN AMINE HAVING FORMULA RHN2 WHEREIN R IS A HYDROCARBON RADICAL OF ABOUT 8 TO 22 CARBONS. 